In the manufacture of integrated circuits, such as semiconductor devices, it is often desirable to form one or more features on the substrate, such as a semiconductor wafer substrate, for identification purposes. For example, in laser marking, laser radiation is used to partially melt and ablate a portion of the surface of the substrate to form a visible feature. These visible features, or indicia elements, are created in patterns to form identifying indicia.
The features generally have the structure of a blind bore or hole as shown in FIG. 1. Because of the shape of the feature, residue such as photoresist can remain in the feature, and the shape of the feature makes it difficult to completely remove the residue. The residue may, under subsequent processing conditions, eject from the feature and redeposit on nearby integrated circuits. Thus, the presence of the residue can adversely affect subsequent manufacturing steps and decrease the yield of integrated circuits on the substrate. As the geometries of integrated circuits continue to shrink, the detrimental effect of residue from laser marking tends to have an increasing impact on the yield.
Another shortcoming of conventional processes is their ability to render features of desirable configuration. For example, to enhance the visibility of the features, it is desirable that the cross sections of the features be substantially circular. Conventional methods may not yield features having such characteristics.
What is needed, therefore, is a method for forming features that have a shape that aids removal of residue from the features and which also renders features of more desirable configuration.